Thread tensioner with improved yawn mechanism

ABSTRACT

An improved sewing machine device for placing tension on the thread having means for developing suitable yawn upon release of tension in the device. The structure includes three adjacent tension discs, through which a tension rod is capable of applying varying degrees of compressive tension against the three adjacent discs. The middle tension disc is of non-magnetic material while the other two tension are discs are of magnetic material and whereby all three discs are loosely carried on a brass arbor. A member of non-magnetic material supports a plurality of bar magnets which reside adjacent the terminating disc of a central rod which passes through the arbor and the discs. When the tension on the rod is released, separation occurs between the three discs in order that a thread or threads may be properly inserted between any two of the three discs. When this tension rod is released, the effect of the magnets is to attract the magnetic discs away from their previous compressed positions so as to cause a space separation between the discs and into which may be readily inserted a thread or threads.

United States Patent [1 1 Kuhar 1 Dec. 23, 1975 THREAD TENSIONER WITH IMPROVED YAWN MECHANISM Ludwig John Kuhar, Clark. NJ.

[73] Assignee: The Singer Company, New York,

[22] Filed: Mar. 25, 1975 [21] Appl. No.: 561,749

[75] Inventor:

Primary Examiner-George H. Krizmanich Attorney, Agent, or Firm--Edward L. Bell; Robert E. Smith; Marshall J. Breen [57] ABSTRACT An improved sewing machine device for placing tension on the thread having means for developing suit able yarn upon release of tension in the device. The structure includes three adjacent tension discs, through which a tension rod is capable of applying varying degrees of compressive tension against the three adjacent discs. The middle tension disc is of non-magnetic material while the other two tension are discs of magnetic material and whereby all three discs are loosely carried on a brass arbor. A member of non-magnetic material supports a plurality of bar magnets which reside adjacent the terminating disc of a central rod which passes through the arbor and the discs. When the tension on the rod is released, separation occurs between the three discs in order that a thread or threads may be properly inserted between any two of the three discs. When this tension rod is released, the effect of the magnets is to attract the magnetic discs away from their previous compressed positions so as to cause a space separation between the discs and into which may be readily inserted a thread or threads.

68 574,52 i j; J6

U.S. Patent Dec. 23, 1975 Sheet 1 of3 3,927,631

Sheet 3 of 3 3,927,631

llllllllIHlllllI|lll\\\\\\\\\\\\\\\\ \\\\\\\\\\\llllllIIIIIIIIIIHIIIII/ll/ US. Patent Dec. 23, 1975 THREAD TENSIONER WITH IMPROVED YAWN MECHANISM BACKGROUND OF THE INVENTION This invention relates to the field of sewing machines wherein thread-tensioning devices are conventionally used to apply friction or drag to the sewing thread or threads. Normally, these thread tensioning devices in sewing machines are arranged so that tension in a device is released in order to permit the insertion of a thread or threads, after which tension is applied to the threads in order to develop the proper amount of friction or drag.

In presently constructed tension devices where tension discs are arranged on a supporting arbor, and are biased together against an abutment to apply tension and then are floated freely of axial pressure to release the tension, the discs often do not separate when the axial tension is removed therefrom. In such a case when the thread is laid in the slot against the tension disc, the thread may not drop in between the discs but may lie loosely over the edge of the unseparated discs and never enter properly therebetween. In many cases the tension device is so buried or hidden within the machine that the operator would not know whether or not the thread had fully and properly entered between the tension discs with a result that improper stitching could occur.

The present embodiment provides a way in which the thread tensioning discs are physically separated (yawn) when the axial pressure is removed. Due to this physical separation or yawn, when the thread is inserted in the slot, it falls between the discs down to the central axis as it properly should. Then when axial tension is applied, the proper amount of drag or friction is provided to the moving thread or threads.

SUMMARY OF THE INVENTION This invention provides a needle thread tensioning device, of an improved design, for a sewing machine constructed and arranged so as not to detract from the operators view of the work being stitched and so as not to compete for space occupied by other mechanisms within the sewing machine, and which at the same time provides for an easy and positive displacement of the thread into the thread tensioning device in such a manner as to eliminate any possibility that the thread will only enter superficially into the tensioning device and hang up on the periphery instead of penetrating all the way into the center section of the tensioning device. The separation of tension discs at the interfaces (to permit thread insertion) is usually denoted as yawn.

The needle thread tensioning device is located in the removable top cover of the sewing machine. This location, unoccupied by any other operating mechanism of the sewing machine, places the exposed portion of the thread tensioning device beyond, or out of the way of the line of sight of an operator who was working on the material being sewn.

The tensioning device of the present invention preferably employs three discs which provide two interfaces into which may be placed a single thread for a single needle sewing machine or two threads for a double needle sewing machine, wherein in the latter case one thread may be placed into each one of the two interfaces.

The three tension discs of the present invention all ride on a cylindrical arbor having a bore in its center through which there rides axially a tension rod. One end of said tension rod is provided with an anchor disk which acts to compress together the three tension discs when tension is applied to the tension rod. If the tension rod is released of its tension, then no compressive force is applied to force together the three tension discs. A mechanism is provided by which it is possible to regulate the amount of compressive tension which is applied to the three tension discs.

A release mechanism is provided which permits all tension to be removed from the tension rod. But, when the tension releasing mechanism is activated, there is no guarantee that the three tension discs will separate sufficiently to permit thread to be inserted therebetween, and it is this desirable condition that is solved by the present invention. Upon release of all tension on the central rod (and thus on the three tension discs), an adjacent set of bar magnets are used to pull apart and separate the tension discs from their previously compressed position. This occurs due to the fact that the central disc is made up of non-magnetic material while the extreme discs are made up of magnetic material. It will be understood that non-magnetic material is any material not capable of being magnetised and that magnetic material is any material capable of being magnetised. Thus, when the compressive tension on the three discs is released, the adjacent set of magnets will thus pull the closest magnetic disc toward it with a considerable magnetic force and at the same time will exert a little force upon the other extreme disc to loosen it slightly from its prior position.

The overall effect of releasing the compressive tension on the tension discs, is to then allow the magnetic field of the magnets to separate the three tension discs and thus to provide wider interfaces (yawn) between them so that when the thread is inserted into the tension device it will properly reach down into the center area of the interface and not merely hang up superficially on the periphery of the interface.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the thread tensioning device of this invention with the removable top cover of the sewing machine shown in phantom lines.

FIG. 2 is an exploded perspective view of the thread tensioning head of the device.

FIG. 3 is an enlarged bottom plan view of a portion of the sewing machine top cover with the thread tensioning head illustrated in cross-section.

FIG. 4 is a front elevational view of a sewing machine having the invention applied thereto, and with portions of the machine frame broken away to illustrate the tension releasing mechanism.

FIG. 5 is a cross-sectional view taken substantially along line 5-5 of FIG. 3.

FIG. 6 is a cross-sectional view taken substantially along line 6-6 of FIG. 3; and

FIG. 7 is a cross-sectional view taken substantially along line 7-7 of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 4,.this invention is illustrated as applied to a sewing machine having a bed 11 and a bracket arm 12 overhanging the bed and terminating in a sewing head 13. Preferably the bracket arm and sewing head are hollow and are provided with an opening at the top adapted to be closed by a top cover plate 14 which is removable and may be fastened to the bracket arm by any suitable means. A reciprocatory needle bar 15 is joumaled in the sewing head 13 and has a thread carrying needle 16 secured at its lower end by a clamp device 17. The needle bar 15 and the needle thread take-up arm 18 having a thread eye 19 closely adjacent thereto are imparted reciprocatory movements in concert by a drive mechanism (not shown) in the bracket arm.

The needle thread tensioning device of this invention is carried by the removable top cover 14 of the sewing machine frame. The needle thread tensioning device includes a thread engaging head 20 which extends exteriorly of the top cover closely adjacent the path of movement of the take-up am 18. Also projecting exteriorly of the top cover 14 alongside the thread engaging head 20 is an operator influenced tension adjusting dial 21 which, as will be described hereinbelow, serves to regulate the tension which is imparted to the thread by the thread engaging head. As shown in FIG. 4, a needle thread N is directed from a supply spool (not shown) to the thread engaging head 20 and to the influence of the elements thereof which will be described in greater detail below, thence downwardly about a thread guiding post 22 which is set into the sewing head and may be formed with a thread detaining skirt 23. The thread guiding post 22 is arranged beneath the path of motion of the take-up arm 18 to the eyelet 19 of which the thread is directed from the thread guiding post. From the take-up arm the thread is directed downwardly to the sewing machine needle 16. Portions of the sewing head, the top cover 14, and portions of an end cover plate 25 have been broken away in FIG. 4 along with portions of the needle bar 15 and driving mechanism of the sewing machine in order to expose a presser bar 26 which is carried in the sewing head parallel to the needle bar 15. A work engaging presser foot 27 is secured to the lower extremity of the presser bar as by a clamp screw 28 and a downward biasing force may be applied to the presser bar by a plunger 29 slidable in an axial bore in the presser bar and constraining a spring (not shown) therein. A rotary cam 30 pivoted in the sewing head serves to regulate the downward pressure exerted by the presser foot. Secured to the presser bar 26 as by a set screw 31 within the sewing head 13 is a block 32. An operator influenced presser lifter lever pivoted on the sewing head 13 includes a cam portion 36 beneath the block 32 which may raise and lower the presser foot. A vertical rod 33 with a reduced upper extremity 34 is constrained by a clip 37 in a clearance bore 38 in a web 39 of the bracket arm and extends downwardly into engagement with the cam portion 36 of the presser lifting lever to serve for releasing the tension which is applied to the needle thread by the thread engaging head 20 whenever the presser lifting lever 35 is operated.

Referring particularly to FIG. 3, which illustrates the thread engaging head 20 in cross-section, and to FIGS. 1 and 2 which illustrate the assembled and exploded views of the thread engaging head in perspective, the details of construction of the thread engaging head 20 will be described. A central arbor 40 is provided which is formed at one end with a transverse slot 41 having external threads 42. Between its extremities, the arbor 40 is formed with an annular flange 43 (FIG. 2) and an axial bore 44 (FIG. 3) is provided in the arbor extending from the transverse slot 41 to the opposite extremity of the arbor. A sleeve 45 (FIGS. 2 and 3) is secured by a press fit on the arbor 40 at the opposite side of the flange 43 from the transverse slot 41 and serves to confine against the flange 43 a thread guiding bracket 46. The thread guiding bracket 46 is formed with a rotation restraining finger 47 which, as shown in FIG. 4, fits into a notch in the top cover 14. At each side of the rotation restraining finger 47, the thread guiding bracket 46 is formed with contiguous oppositelydirected thread-guiding notches 48 and 49 (FIG. 2) which accommodate the incoming and outgoing limbs respectively of a loop of thread which is directed to the thread engaging head.

Referring particularly to FIG. 2, there is carried, on the transversely slotted extremity 41 of the arbor 40 (against the flange 43), preferably three tension discs 50a, 50b and 50c at the opposite side of which is provided an anchor disc 51 which is the terminating endpart of the rod 54. The anchor disc 51 is provided with a diameter bar 52 which enters the slot 41 in the arbor 40.

The thread tension discs 50a, 50b and 500 have central apertures permitting them to ride on the slotted end of arbor 40 beyond flange 43. The central disc 50b is made of non-magnetic material, such as brass, while discs 50a and 50c are made of material subject to the influence of a magnetic field.

The rod 54 is movable through the axial bore 44 (FIG. 3) of arbor 40, and is connected to the diameter bar 52 of the anchor disc 51. The rod 54 is thus slidable axially in the bore 44 of the arbor 40. A directional force, therefore, applied lengthwise along the axially shiftable rod 54 will impart pressure on the discs 50a, 50b and 50c.

Threadedly engaging the threads 42 on the arbor 40 is a cup-shaped member 56 (FIG. 2 and FIG. 3) which serves to constrain the anchor disc 51. Situated within the inside cup of the cup-shaped member 56 is a group of three magnets 57a, 57b and 570 which are fixedly fastened at equal intervals around the inner periphery of the cup-shaped member 56.

By turning the cup-shaped member 56 on the threads 42, a regulation of the overall allowed travel of the rod 54 and anchor disc 51 is arranged.

The cup-shaped member 56 also provides a reception seat for a coil 58, at one extremity of a wire check spring 60.

A wire check spring 60 is formed with a plurality of coils 61 which are accommodated on the sleeve 45, and the intumed extremity 62 (FIG. 3) of the check spring coils 61 is anchored in a transverse slot 63 formed in the sleeve 45.

A washer 65 (FIGS. 2 and 3) is provided on the arbor 40 against the cup-shaped member 56 and a cover member 66 is secured against the washer 65 by a threaded nut 67 engaging the threads 42 on the arbor. The cover member 66 (FIG. 3) is formed with a skirt 68 which together with the skirt 69 on the thread guiding bracket 46 shrouds the thread tension discs 50a, 50b and 50c.

Referring to FIG. 3, the top cover 14 is formed with a recess 80, providing a reception seat into which the arbor 40 is accommodated and locked in place by a set screw 81. The recess is preferably large enough to accommodate the sleeve 45 and the coils 61 of the check spring.

The organization of the mechanism for imparting and regulating pressure between the thread tension discs 50a, 50b and 50c so as to impart tension to a sewing thread is best illustrated in FIGS. 1 and 3. This tension influencing mechanism is carried interiorly of the top cover 14 above the bracket arm 12 and in a space which is not ordinarily occupied by an operating mechanism of a conventional sewing machine. Secured by a fastening'screw 90 beneath the cover plate is a bracket 91 formed with a tang 92 which may engage a projection 93 formed beneath the top cover to prevent tuming movement of the bracket 91. Threaded in a pair of spaced arms 94 and 95 on the bracket 91 is a mandrel 96 formed with a plain cylindrical extremity 97. A coil spring 98 which is constrained on the plain cylindrical extremity between abutment washers 99 and 100 thereon provides the spring pressure which will be applied by the mechanism now being described to bias the thread tension discs together.

The force of the spring 98 is transmitted to the rod 54 by a rigid lever l preferably having a U-shaped crosssection as best illustrated in FIG. 7. The lever 110 is formed with an aperture 1 l l embracing the plain cylindrical extremity 97 of the mandrel 96 and a pair of projections 112 may be struck out from the lever 110 to engage the washer 100 substantially along the center line of the mandrel 96. The lever 110 at the opposite extremity (FIG. 5) is formed with an aperture 113 through which the rod 54 extends. As best illustrated in FIG. 5, a head 1 14 formed on the rod 54 is smaller than the main portion of the aperture 113 and can be inserted therethrough, however, a narrow lateral portion 115 of the aperture 1 13 is smaller than the head 1 14 of the rod and serves to lock the rod 54 to the lever 110 when the head 114 is releasably detained therein by a spring clip 116 snapped into position across the main portion of the aperture 113. The spring clip 116, as shown in FIG. 6, preferably extends through openings 117 therefor in the lever 1 10 and includes a spring clip portion 118 (FIG. 6) folded back upon itself yieldingly to engage of the lever 110 to retain the spring clip 116 in place.

A fulcrum is provided for the lever 110 by means of a pair of laterally extending fulcrum fingers or projections 120 (FIG. 7) carried by a slide member 121 which preferably includes a U-shaped portion nested within the U-shaped section of the lever 110 as illustrated in FIG. 7. The slide member 121 is constrained for a substantially rectilinear movement by a lengthwise guide slot 122 (FIG. 3) which embraces a shouldered pivot pin 123 which is screw threaded into the top cover 14 and by a guide abutment 124 which is formed interiorly of the top cover 14 at the opposite side of the slide member 121 from the lever 110. The tension regulating dial segment 21 is joumaled for turning movement on the pivot pin 123 and projects outwardly of the top cover through a slot 125 therein. A crank pin 126 projecting from the dial segment 21 is embraced in a slot 127 formed in the slide member 121 substantially at right angles to the guide slot 122. By this arrangement turning of the dial segment 21 will, by way of the crank pin 126, shift the slide member 121 to move the fulcrum projections 120 along the lever 110. The position of the parts as shown in FIG. 3 illustrates the fulcrum projections located directly opposite the axis of the mandrel 96 so that the pressure of the spring 98 is completely removed from the rod 54. As the fulcrum projections 120 are moved toward the rod 54 along the lever 110, the lever arms will be changed to impart an increasingly greater component of the pressure of the spring to the rod 54. The threaded mandrel 96 may be turned in the spaced arms 94 and of the bracket 91 to regulate the pressure of the spring 98 which will vary the entire range of pressure settings applied to the thread by the thread engaging head 20.

The pressure of the spring 98 may be removed from the thread tension discs 50a, 50b and 500 whenever desired by a tension release lever 130 which is fulcrumed on a rivet 131 secured into a bracket 132 which is secured beneath the top cover 14 by a fastening screw 133. The bracket is further stabilized beneath the top cover by a slot 134 therein which embraces a downward projection 135 from the top cover.

An offset lever arm 136 (FIG. 4 and 6) on the tension release lever 130 overlies the reduced upper extremity 34 of the vertical rod 33 (FIG. 4) which is operated by the sewing machine presser lifting lever 35. A lever arm 137 (FIG. 3) disposed adjacent the spring force transmitting lever serves, when the presser foot 27 (FIG. 4) is lifted, to shift the lever 110 toward the thread engaging head 20 and thus to remove the pressure of the spring 98 from the thread tension discs 50a, 50 and 500.

OPERATION Since the major problem to be solved in this embodiment is the placement of a thread or threads between the frictioning discs 50a and 50b, or, on the other hand, placing the thread between the frictioning discs 50b and 500, in such a manner that the thread will fall completely to the center portion between the discs sothat the peripheral edges of the discs may frictionally engage the thread to impart the proper amount of tensioning on the thread (as the thread is moved through and between the frictioning discs).

The problem arises in that the interfaces between the discs 50a, 50b and 50c will not ordinarily appear to the naked eye or even yawn to any extent unless some external means is provided to insure that sufficient space will occur between 500 and 50b, and also between 50b and 500 so that the inserted thread will fall into the central axial area between the discs.

In the present embodiment the tension regulating dial 21 is adjusted to impart a certain amount of spring pressure on the rod 54 such that the anchor disc end piece 51 of the rod 54 will cause a tightening or pressure as between the tension discs 50a, 50b and 50c. Now, however, when the pressure on the rod 54 is released, and it is desired to insert new threads as between the discs 50a, 50b and 500, the bar-type magnets 57a, 57b and 57c play a role to insure sufficient yawn.

Thus, when the tension release lever is used to remove the tension, then lever 110 will be moved by arm 137 downward and away from the head 1 14 of rod 54, so as to release rod 54 so that rod 54 floats loose axially within the bore 44; and thus, anchor disc 51 is no longer compressing the tension discs 50a, 50b and 50c.

Since the disc 500 is a magnetic disc while 50b is a non-magnetic disc, it will be seen that the action of the bar magnets 57a, 57b and 57c will be such as to pull away or draw the disc 50c away from the non-magnetic disc 50b so as to open a gap (yawn) as between 50b and 500. With the occurrence of this gap, it will then be easy for the thread to be inserted between 50b and 500 after which the tension release lever 130 may be released and lever 110 can then resume applying tension to rod 54 through head 114 so thatj the appropriate ,t@nsin discs mounted on said arbor and between friction and tension will be applied to the flir'e'ad which had been inserted between 5012 and 50c.

Since the disc 50a is of magnetic material, it will be partially withdrawn away from the flange 43 of the arbor 40 during the time that the tension is released on rod 54. However, since 50a is separated by a greater distance from the three magnets and since 5017 is of non-magnetic material, there will only be a slight movement of disc 50a, but this will be sufficient to cause a jar as between 50a and 50b to increase the distance between 50a and 50b. in other embodiments, a second set of magnets could be anchored to flange 43 to provide greater yawn for the interface between disc 50a and 50b.

The above description defines and the drawings illustrate a tension assembly in which there are three tension discs 50a, 50b and 500, whereby two sewing threads can be used when a sewing machine is fitted with a conventional twin needle. However, it will be realized that the present invention can be incorporated in a tension device have only two tension discs, one of magnetic attractable material such as disc 50c and one of non-magnetic material such as disc 50b.

Thus, there has been described a mechanism for the application and loosening of tension between adjacent tension discs with the proviso that when the tension as between the discs is released, the nearby application of adjacent bar magnets will act such as to separate the spaces between the formerly compressed discs so that substantial yawn will occur as between the discs upon the release of tension on the rod 54. Subsequently, when the tension is applied back again to rod 54, the discs will be compressed according to the amount of tension set by the regulating mechanism and the magnetic effects will no longer be active to separate the discs.

Having thus set forth the nature of the invention, what is claimed herein is:

1. A thread tension device for sewing machines comprising an arbor, at least one pair of thread engaging which needle thread is adapted to pass, one of said tension discs being formed of a non-magnetic material and a second of said tension discs being formed of magnetic material, spring means for biasing said tension discs together thereby to apply tension to the thread passing between them, means for releasing said spring means, and magnet means disposed in relation to said tension discs to cause said tension discs to separate upon actuation of the spring release means.

2. A thread tension device in accordance with claim 1 in which the magnetic means includes at least one magnet, and a magnet supporting member mounted on said arbor with said at least one magnet positioned closely adjacent the tension disc formed of magnetic material.

3. A thread tension device in accordance with claim I in which there are at least three tension discs mounted on said arbor, said tension discs including a disc of non-magnetic material straddled by two discs of magnetic material.

4. A thread tension device in accordance with claim 2 in which said magnet supporting member comprises a cup-shaped element threadedly mounted on said arbor in position adjacent to said magnetic disc and supporting at least a pair of magnets within the rim portion thereof.

5. A thread tension device for sewing machines comprising an arbor, a first thread engaging tension disc, a second thread engaging tension disc made of magnet material and freely mounted on said arbor for movement longitudinal of said arbor, spring means for biasing said second thread engaging disc toward said first thread engaging disc for exerting tension on thread passing between said discs, means for releasing said biasing means, and magnetic means effective to cause said second thread engaging disc to separate from said first thread engaging disc upon actuation of said biasing means releasing means. 

1. A thread tension device for sewing machines comprising an arbor, at least one pair of thread engaging tension discs mounted on said arbor and between which needle thread is adapted to pass, one of said tension discs being formed of a non-magnetic material and a second of said tension discs being formed of magnetic material, spring means for biasing said tension discs together thereby to apply tension to the thread passing between them, means for releasing said spring means, and magnet means disposed in relation to said tension discs to cause said tension discs to separate upon actuation of the spring release means.
 2. A thread tension device in accordance with claim 1 in which the magnetic means includes at least one magnet, and a magnet supporting member mounted on said arbor with said at least one magnet positioned closely adjacent the tension disc formed of magnetic material.
 3. A thread tension device in accordance with claim 1 in which there are at least three tension discs mounted on said arbor, said tension discs including a disc of non-magnetic material straddled by two discs of magnetic material.
 4. A thread tension device in accordance with claim 2 in which said magnet supporting member comprises a cup-shaped element threadedly mounted on said arbor in position adjacent to said magnetic disc and supporting at least a pair of magnets within the rim portion thereof.
 5. A thread tension device for sewing machines comprising an arbor, a first thread engaging tension disc, a second thread engaging tension disc made of magnet material and freely mounted on said arbor for movement longitudinal of said arbor, spring means for biasing said second thread engaging disc toward said first thread engaging disc for exerting tension on thread passing between said discs, means for releasing said biasing means, and magnetic means effective to cause said second thread engaging disc to separate from said first thread engaging disc upon actuation of said biasing means releasing means. 